Juckes MN et al. 2007: Millennial temperature reconstruction intercomparison and evaluation, Climate of the Past, 3: 591-609

Dall'abstract:


[...] A range of proxy data collections introduced by different authors is used to estimate Northern Hemispheric annual mean temperatures with two reconstruction algorithms: (1) inverse regression and, (2) compositing followed by variance matching (CVM). It is found that inverse regression tends to give large weighting to a small number of proxies and that the second approach (CVM) is more robust to varying proxy input. The choice of proxy records is one reason why different reconstructions show different ranges.
Proxy:


CVM:


Inverse Regression:


Dalla conclusione:

There is general agreement that the warmest pre-industrial temperatures of he last thousand years occurred at the start of millennium, and the coolest at some point during the 16th to 19th centuries. There is also general consensus that the warmest pre-industrial temperatures were close to the mean of the 20th century.[...]
The IPCC 2007 conclusion that “It is very likely that average NH temperatures during the secon d half of the 20th century were warmer than any other 50-year period in the last 500 years and likely the warmest in at least the past 1300 years” (Solomon et al., 2007) is also supported by our analysis.